


The Work of a Scientist

by slimesurgeon



Category: Undertale (Video Game)
Genre: Implied Age Difference, Knotting, Office Sex, Oral Sex, Other, Penetrative Sex, Pre-Accident W. D. Gaster, Reader-Insert, Romance, Teasing
Language: English
Status: Completed
Published: 2018-12-18
Updated: 2018-12-18
Packaged: 2019-09-21 21:05:10
Rating: Explicit
Warnings: No Archive Warnings Apply
Chapters: 2
Words: 8,792
Publisher: archiveofourown.org
Story URL: https://archiveofourown.org/works/17050556
Author URL: https://archiveofourown.org/users/slimesurgeon/pseuds/slimesurgeon
Summary: You're Gaster's assistant, and his well cared for human subject for scientific research. He's intellectual, shy, and charming--and you have the hardest time containing your burning hot feelings for him.*This fic features my own personal design for pre-accident Gaster, which is a skeleton monster a bit canine like with a muzzle, horns, and a tail, (think: Gaster Blasters)*-Reader is ambiguous gender with ambiguous genitals.-Penetrative sex on reader.-Gaster has a knotted penis.





	1. Chapter 1

**Author's Note:**

> Hello! It's me, Slime! I've chosen to archive all of my fics here on ao3, since they are now deleted from tumblr. 
> 
> This is another fic from 2017. Probably my favorite one. This was the fic I started getting more comfortable with my writing, and I think it still holds up pretty well! Hope you enjoy!

It was 4:00 am, and you were brewing Dr. Gaster's fifth cup of coffee. Or was it the sixth? It could have been the seventh; you had lost count. You knew he wasn't keeping track either. He'd typically go through two pots himself on nights like this. He was hastily scribbling down notes and sketching blueprints, his eyes never leaving his work even as you set his mug back down on his desk. He uttered a “thank you,” as always, and you simply smiled and nodded your head despite the fact he wasn't looking at you. You didn't want to distract him.

 

You went back to tidying his office. Actually, you finished that task hours ago. Gaster never looked up from his work to notice that you'd been sweeping the already pristine floor or “sorting” files by picking them up and putting them back down in the same spot. He dismissed you from your work long ago, but you had insisted on cleaning some more. Truthfully, you wanted to spend all the time you possibly could with him while he was alone, even if it meant refilling coffee and pretending to be busy in the meantime.

 

You wished you could help him, though you could never begin to understand his work. You didn't need to. As a human test subject, all you needed to do was lend him your body for whatever research he had planned. Sometimes it was painful, but nonetheless exciting. Gaster seemed so emotionally aloof, it was nice getting the little contact with him you did, even if it was something as simple as cleaning your skin with an alcohol wipe before sticking you with a needle. He'd always thank you for a job well done, not that you really knew what exactly you helped him accomplished.

 

A long yawn from Gaster snapped you back to attention. He was blinking tiredly, his glasses sliding further from his eyes and down his snout. You hurried to his desk to take his mug for another refill, but he waved you to stop. “No, that's alright,” he pushed his glasses back in place, “I think I'm done for the night. I've hit a snag and I think I'll be better of having a fresh look at it tomorrow...” he glanced at the clock on the wall. “...Later today, rather.”

 

“What's the problem?” you asked instinctively, looking down at the paperwork written in an alien language.

 

“Well, in theory, it should be possible to extract 'determination' from a human soul within its vessel, which would mean- ” Gaster gave you a long-winded explanation filled with words and numbers you quickly lost track of. You stared at him absentmindedly. Despite the fact you didn't know what he was talking about, it was attractive hearing him talk about it. These were the only times you ever heard him talk so passionately about something. At the end of his spiel, you nodded as if you understood. Gaster smiled sympathetically. “I know, it's complicated. I don't expect you to understand.” He was gathering the documents on his desk in attempts to tidy the chaos.

 

“Oh no, let me-” you reached down at the desk. Gaster gently placed one of his hands on top of yours, freezing you in place.

 

“It's alright. You've done enough. Don't you want to get some rest?”

 

“Well uh... I want to help you...” you were averting your eyes shyly.

 

Gaster curled his clawed fingers and let your hand go. He chuckled under his breath. “There's no arguing with the determination of a human...” He seemed amused as he flipped through his notes for a moment. It caught you off guard, causing you to remain frozen where you were, forgetting that you were about to tidy up the papers. Instead, you watched his beady white pupils dart left and right as he sifted through his notes thoughtfully.

 

“Hmm... Could I make a presumptuous request?” Gaster looked up at you, over the rims of his glasses.

 

“O-Of course.” your hands dropped to your sides and you straightened your posture.

 

“May I look at your soul for just a moment? It will be very quick. I know it's not very professional to do it here, but it would help me greatly if you would allow it.”

 

Typically, when your soul was being examined, you were comfortably rested on an operating table in the lab. It wasn't a painful of grueling process though, so you had no qualms with doing it quickly. “Yes, of course, Doctor.”

 

Gaster pushed himself backward in his chair to make some space, and he patted the edge of the desk in front of him. “You can sit right here. I won't take long.”

 

You timidly approached him, inching into the little space between him and the desk. Your heart was already racing being this close to him so casually. You shooed away the thought invading your mind about how you could easily sit down on his lap then and there. It made your stomach feel hot. You obediently sat on the desk, praying internally you weren't blushing.

 

Gaster didn't seem to notice anything though, as he was already conjuring his familiar purple magic, letting his hand hover an inch from your chest. There was a warm tingly feeling as it pulled your soul gently forward, making it visible to the both of you. It was translucent and phantom-like, and your favorite color. You've seen it before, and you've felt the sensation before. The difference, though, was that usually you'd be in a clinical setting, with other scientists and machines making noise around you. Now, it was dead silent, and Gaster was the only one there with you. It clearly didn't seem odd to him, as he was scrutinizing your soul closely as usual, and jotting something down on a notepad beside you. But to you, you felt strangely exposed—naked even. This felt intimate and exciting.

 

You squeezed your legs together and curled your fingers into fists on the table. You needed to keep your composure—this was strictly business, not something meant to fulfill your lewd fantasies—but it was difficult. You closed your eyes and waited impatiently for it to be over.

 

The sensation faded almost abruptly. More abruptly though, you heard Gaster's voice shake, “A-Are you alright...?” You opened your eyes to see that Gaster had withdrawn his hands and was fidgeting in front of him. His brow was furrowed and he looked... embarrassed? It was certainly wasn't an expression you'd ever seen him wear.

 

“Y-Yeah! I-I'm fine..!” you stuttered, your heart sinking as all the possibilities of what he could have noticed raced through your mind.

 

You were about to ask him if _he_ was alright, but he quickly interjected, “I'm so sorry. This was inappropriate, wasn't it? I didn't mean to put you in an awkward situation.”

 

He was only making you feel more embarrassed, not knowing what he was referring to. “D-Did I do something wrong..?”

 

“No, no. I just... noticed...” watching his expression lose more and more of its composure was incredulous, “you seemed to be... blushing?” his eyes looked _guilty_. It was shocking. There was no reason that _he_ should be the one feeling guilty. He was averting eye contact from you and shrinking in his chair. It was _cute._

 

You scrambled to think of something appropriate to say, between your infatuation-filled thoughts invading the front of your mind. You felt all too ashamed, and covered your mouth with your hands, averting your eyes just the same.

 

After a minute of silence, Gaster spoke up sheepishly again, “You're not... _interested_ in an old monster like me... are you?” You made eye contact with him again. There was a little purple tint to his cheeks—he was blushing too. You'd never seem him blush before—you weren't even sure he could for that matter—it left your mouth agape in surprise.

 

Losing your sense of restraint for a moment, a “yes” squeaked out of your throat. There was an incredulous stupor on Gaster's face, and you felt like you could die of embarrassment spilling your feelings for him like this. At the same time, it felt _amazing_ getting to see him flustered. You thought that perhaps it could actually be worth it if Gaster fired you right then in there.

 

He seemed too shocked to respond—or even think, for that matter. He was frozen in silence, the purple blush on his cheeks growing. You did it. You brought his genius mind to a halt. Who else has ever done such a thing?

 

Your heart racing with excitement, your inhibitions dropped enough for you to drop down onto his lap, as you wanted to do all this time. As you straddled him, his jaw dropped in astonishment. His hands flung up to his shoulders, palms out, as if afraid to touch you. His legs were trembling under you. There was no turning back now, you knew. You felt regret for a moment, but you pushed that to the back of your mind where the rest of your worries about consequences now hid. The only thing you could do now was act in the flow of the moment.

 

“Doctor, I... really um... I really like you.” you said softly, wishing you could have said something more eloquent than that. You gingerly placed a hand onto his collarbone and slid it up to his shoulder. His eyes darted to and fro from your hand and back to your face. The lavender blush on his face was darkening to plum.

 

“I-I-I don't u-understand... w-why me?”

 

That was an absurd question to you. He was the royal scientist. The most brilliant mind in all of the Underground. Who _wouldn't_ find him desirable? You weren't even sure how to give him that answer without sounding condescending, so you opted for, “I just really like being with you.”

 

Gaster's mouth formed a piteous half-smile. “Y-You're too attractive for an old skeleton...”

 

 _Attractive._ So that's how he felt about you. Your heart felt giddy, and you couldn't stop yourself from smiling big. You placed your hands into Gaster's still-open palms and laced your fingers with his. He hesitantly curled his trembling claws over your knuckles and looked down away from your face timidly. You leaned in towards his snout just short of touching your nose to it. It occurred to you this close that his jaws were certainly big enough to fit your whole head between them, which was just another reason you were so enamored with him—he looked like a voracious beast (at least to a human), but he was a sheep in wolf's clothing.

 

You pressed your lips onto his closed teeth, your heart feeling like it could beat of of your chest. He couldn't quite kiss you back, you knew, but you felt his mouth part just a little bit to let you tongue poke inside. He tasted like coffee.

 

Your hands slipped out of his grip so that you could caress his shoulders and run your fingers up his neck, feeling the little crevices between the bones of his vertebrae. His hands now free, they slowly made their way down until they were hovering over your thighs. He was looking down at them and shyly back to your face. You nodded warmly, and with your approval he made contact.

 

“I think you're really attractive, actually...” you sighed, sliding your hands up the sides of his skull and to the base of his horns. You used those to pull his face closer, prompting him to make room by opening his jaws more. You licked the back of his fangs where ever you could reach, sighing at how pleasant he tasted.

 

Gaster started making some kind of nervous sounds of pleasure himself and his claws were gripping the fabric of your pants. “Oh... hahh...” You were intrigued by the ragged noises he was making—you'd never heard such a thing from him before. Your hands slid up his horns and back down, rubbing them, the motion turning into a rhythm that flowed through you so you could grind on his lap. His head gradually tilted downward further and further until his nose was pointed completely down. Holding his head like this made him look so subdued. He was huffing, and his hands traveled to your waist and dug into the fabric there.

 

“A-Are you s-sure yo-ahh!” Gaster tried to form words between his sighs, but you'd respond by pulling his horns down more and grinding harder into his lap, so you could cherish his precious moans. “Y-You could do b-better than me-eeyaah! O-Oh, ah!”

 

You suddenly felt something hard beneath your crotch; you had no idea Gaster even _had_ a penis but you knew it was certainly that, which was all the better. He noticed the moment that you did, and he seemed morbidly embarrassed, quickly throwing his hands over the seat of his pants to hide his boner.

 

“Oh no! I-I'm sorry!” his eyes were wide and pleading. You tried to give him a comforting smile as you slipped your hand beneath his to search for his zipper.

 

“May I please...?”

 

Gaster hesitantly picked up his hands and put them over his mouth. He nodded timidly. You opened his fly and pulled his cock through. You were stupidly surprised it wasn't exactly like a human penis, but then again, you weren't sure when to expect when it came to monster genitals. It was purple like his magic, and translucent as though it were made of something like gelatin. It wasn't much longer than a human's, but it was thick, and had a knot at the bottom. By now, you felt your own arousal dripping at the thought of what a cock like that might feel like inside you.

 

“It's beautiful..” you cooed, rubbing your fingers gently along the shaft. It was warm and soft. Gaster was glancing to and from your hand, your face, and away from everything frantically. His hands were now gripping the sides of his chair, scratching restlessly upon the underside. Beads of sweat were forming on his forehead and quickly ended up rolling off his face.

 

“I-I never thought that a human c-could... b-be attracted to... hnnnnn... It's i-interesting...”

 

It was so cute how he was trying to talk science, while your had your fingers curled around his cock. You sandwiched it in your thighs, rubbing it between them, as your fingers played with the tip and made it twitch. “W-Would you like make further examinations?” You couldn't believe you got those words out.

 

Gaster's hands flew back onto his face and over his eyes. His claws scraped down the sides of his skull as his breaths became even more desperate sounding. “O-Oh god... yes...” You got off him and stood in the small space between him and the desk behind you, as to take off your pants. You took your sweet time doing that of course, indulging in how Gaster's pupils followed them roll down your legs as though he was watching something magnificent. His hands were fidgeting with the knot of his tie until it came undone, exhaling hot breath. Next your underwear came down. You trembled at first, feeling your genitals become exposed, but sliding them off your legs was easy thereafter. Gaster's eyes were wide as they studied your exposed sex for the first time. You felt a little self conscious as you waited for him to react somehow, but he seemed to be struck speechless.

 

“What do you... think...?” you prompted, smiling nervously.

 

Gaster snapped to attention, making eye contact with you. “I-I have... never gotten the chance to see... this part of human anatomy so closely and... I think it is intriguing.” he folded his hands upon his lap. You struggled to hold back giggling at his attempt to sound professional; you figured it was the only way he knew how to talk about it. He didn't seem like he knew anything about dirty talk.

 

“Would you like to take a closer look?” You spread your legs over his, this time positioning yourself above his cock. Gaster's hands plopped onto the bridge of his snout, and you could swear you heard him whimpering as he nodded. You readied your entrance with your fingers and you positioned yourself onto the tip of his cock, parting them as you very slowly lowered yourself onto it. You moaned as the tip pushed snugly inside you.

 

Gaster's voice was trembling, “Hah..Hahh...” His eyes were half lidded as he watched the length of his cock slowly disappear inside you, until you were above the knot. You were panting and drooling already, already feeling full from the girth. You were determined to take all that gorgeous monster cock inside you however, and so you pushed yourself down further. You clutched Gaster's horns to keep yourself steady, unable to focus on anything but the feeling of being stretched to your limit until finally you felt yourself close again around the smaller base.

 

“Oh god! Doctor it feels so good, oh my god...!” you gushed, your body melting into his and pulling his head down with you. You hadn't noticed until now he was panting so rapidly, you would have thought he was hyperventilating in a bad way until his breaths became ragged moans, with “oh my god”s sprinkled in between. Abruptly, his hands caressed the bare skin of your thighs, his pupils following his exploration through his squinted eyes.

 

“Y-You're marvelous... ohhh, human!” you felt him begin to buck just a little bit below you, and you promptly took your cue to move your hips and ride him in a fluid rhythm. You cooed and moaned in delight; his cock was soft enough that it didn't feel painful at all despite how snug it was against your walls, but full enough to stimulate you. Gaster was losing his composure more and more as he began to moan louder, containing words that you recognized as his unique language, though you could not understand them. His claws dug into your skin as they slid up and down your sides, scratching the surface of your flesh, and leaving pleasantly tingly trails where they grazed.

 

Your hands hadn't yielded their grip on Gaster's horns; instead, you used them to pull yourself up and down on his cock. You couldn't move yourself much more than an inch, however, due to the knot which had swollen even larger inside you. You were locked onto him, and that drove your arousal higher.

 

“More, please more!” you begged, pulling him by the horns close enough to touch noses. Gaster responded by suddenly hoisting you up, his cock still deep inside, and gently laying you down on his desk—atop papers and all—so he could thrust into you while standing.

 

“O-Oh, Doctor, your blueprints-”

 

“Don't worry about it.” his voice became guttural as he hunched over you, sweat dripping off his forehead and into yours. His claws pinned your arms down, which finally forced you to let his horns go. “P-Please... Please call me Gaster...”

 

“Yes, Gaster!” you smiled blissfully, his name tasting so sweet finally getting to say it.

 

It was clear he loved it too from the way he pumped you faster. Despite speeding up though, he was still so gentle pushing in and out of you the little length his cock would allow. Even the little movement felt like so much to you; you were feeling the very beginning of your climax.

 

“Y-You're so warm... it f-feels incredible...” he trailed off into more of his language you couldn't understand, and finally to incoherent moans. It seemed that he was also getting close, from the way his claws dug into your sleeves enough to tear the fabric and graze your flesh. Although you weren't sure if it was an accident or not, it felt so feral, and gave your stomach butterflies. The fact that he fucked you so gently despite his capacity to tear you and bruise you with ease was erotic and adorable.

 

“Oh Gaster... I love this...”

 

His open maw loomed close to your face, exhaling hot breath on you. It was then that his glasses finally fell off his snout and somewhere onto your face, and then onto the desk. He didn't bother to retrieve them. You licked his mouth again, and this time, a big, purple tongue licked you back across your entire face. It was magic and squishy—much like his penis—but it was coated in a sticky lavender saliva that stuck to your face and cooled it. He licked you down to your neck and nibbled it. You were impressed how quickly he picked up intimacy in the heat of the moment.

 

“Ahh, Gaster, I'm gonna come soon!” you moaned. You wanted to touch yourself, but you couldn't lift your arms under his grip. “P-Please, ahhh, touch me so I can come..!”

 

Gaster obediently moved one of his hands to your crotch, looking down at it as he tried to figure out how he should go about the task. He fumbled at first, trying to position his hand in a way that his claws wouldn't hurt you. That itself was admittedly very hot, and you pondered if watching that alone would bring you to climax. Soon enough he succeeded finding the right position, however, and he stroked you gently, his claws just barely grazing your skin enough to send shivers of pleasure up your spine.

 

“Oooooh god! Yes!” you cried, “Gaster, ohh, that's perfect!” with your free hand, you took hold of his lab coat and tugged at it, sating your need to grip onto something as the heat of your orgasm bubbled up and burst through your body. It was enough to make your curl your toes and practically screech in pleasure. You tugged the fabric in your grip forcefully enough to pull Gaster onto your chest.

 

“Please, please, come inside me! Please oh please Gaster!” you moaned raggedly, your climax still tingling. He kept his rhythm, panting heavily, and it was only a few seconds later that he whined in some animalistic way and you felt him release inside you. It felt warm, and filled you deep. Still chest-to-chest, Gaster laid his head down in the crook of your neck as he panted, his cock twitching as his orgasm fizzled away. Your heart was beating hard; Gaster had no heartbeat to match. You wondered if he could feel yous, and if it felt alien to him.

 

After a few minutes of catching his breath, he pulled himself up and withdrew his cock from you, which slid out easily, no longer swollen. Some ejaculate spilled out from your hole and onto whatever document was below, which made Gatser grimace.

 

“I-I'm sorry..!” you began to sit up, but a hand to your chest ushered you gently back down.

 

“No, no. That's my fault. I was careless.” For you, his expression was tender. “Let me clean you up.” After fixing his pants, he disappeared into the lab for a moment, returning with a damp towel to wipe the mess between your legs. He we gentle, taking care to even clean the dried saliva off your face. After helping you into your pants, you looked good as new, save for your ripped shirt. Gaster frowned at it.

 

“I'm dreadfully sorry about that... Do you want to borrow my coat going home?” he didn't wait for you to answer before he started taking his lab coat off. You nodded approvingly and he draped it around your shoulders. It was big on you, and it smelled subtly of chemicals—what Gaster smelled like. You were blushing and smiling, swinging your legs excitedly from the edge of the desk.

 

Gaster fixed his glasses back on his face, looking down in silence as he seemed to be thinking about something. His cheeks were still a little flushed. You let him take his time.

 

“Sh...Shall I walk you home?” his gaze didn't leave the floor.

 

“That would be really nice, Gaster.”

 

He looked at you then, wearing a sheepish smile. He helped you down from the desk, and you both went on your way.

 

Gaster was silent the entire way back. He didn't look at you much either. You could tell that he was lost in thought again, and so you didn't bother to press him for conversation. It was delightful enough having him escort you home for the first time; you were just short of skipping instead of walking, clutching onto the sleeves of Gaster's coat tight. The thought of consequences reared its ugly head in your mind finally, and you pondered the possibilities. Considering Gaster actually _had sex_ with you, it seemed unlikely that he'd be off-put by your confession of feelings. Still, you were unsure. Gaster was not an easy person to read emotionally.

 

When you arrived at your door, you shyly thanked him again for walking with you and wished him a good day. You began reaching for your keys in your pocket, when Gaster finally spoke up.

 

“I wanted to ask you something.”

 

You turned to face him again; he seemed undoubtedly anxious. “Mhm?”

 

He looked down.“Would be interested...” his head lowered more, “sometime...” he could barely stammer this question out, “i-in a date?” He looked at you , his expression absolutely piteous. All that professional demeanor you witnessed day after day in the lab, and yet, this is what you reduced him to.

 

You had to hold back from simply screaming in joy. He just asked you on a date. _The royal scientist_ just asked you on a _date._ “Y-Yeah! I would!” You were beaming, despite your efforts to suppress your obvious over excitement.

 

Gaster's worried frown turned into a something of disbelief, and then a smile. His eyes were wide and his cheeks quickly turned purple. He fidgeted—straightening his tie, rubbing the back of his head, fixing his glasses. “I-I see. That sounds good, then. I-In that case I'll follow up with you about it tomorrow... I'd like you to take the day off today and get some rest.”

 

You nodded. “Yes, sir.”

 

“H-Have a good day.” he quickly ended the conversation to turn in a hurry and briskly go on his way. With him out of sight, you nearly collapsed on your door as you opened it and stumbled inside, your heart a-flutter.

 

You did just as he said and took your day off relaxing, which consisted mostly of lying on your bed and snuggling Gaster's coat. Despite that, though, tomorrow couldn't come quick enough for you. You already couldn't wait to see him again.

 


	2. The Date

**Summary for the Chapter:**

> Dating the royal scientist is no menial affair. 
> 
> -Same content notes apply from Ch 1.

Saturday. That's the day Gaster had decided your date with him would be. The work week until then went by slowly, and uneventfully. You actually hadn't seen Gaster much in the lab during the week. When you were needed for a test, his lab assistants took care of you, and forwarded data and samples to Gaster. As per usual though, your main duties were wiping up spills and going on coffee and doughnut runs for the scientists. Which, of course, wasn't bad at all, but it had you wondering if Gaster was avoiding you. In fact, you were pretty sure he was when he didn't come by for a doughnut. You weren't upset by it though; what happened was rightfully overwhelming. It was natural that he could use some space. 

When Saturday did finally come, you spent a good chunk of your day trying to decide what to wear. You didn't want to seem flashy, but you didn't want to be under-dressed either. This was your first date with a monster, which was daunting by itself let alone him being a very important monster. When you finally did pick something out, the rest of your wait consisted of watching TV and trying to restrain yourself from looking at the clock every ten minutes. He said he would be there at 5:00. 

At 5:01, there was a knock at your door. You loved a man who was punctual. 

You rushed to the door, composing yourself along the way, taking a deep breath in and out before you opened it. It occurred to you immediately that you'd never seen Gaster without a collared shirt and a lab coat—it was almost jarring seeing him something as simple as a grey turtleneck sweater. Nonetheless, he looked quite dashing, aside from his obvious tells of nervousness. His arms were folded behind his back and his shoulders were a bit hunched, his head down slightly so that he was looking at you over the rims of his glasses. 

“H..Hello. It's nice to see you.” 

“It's nice to see you too.” You smiled warmly. You sure did miss seeing him the whole week. 

“You look... very nice.” Gaster was scanning you up and down fondly. 

“Thanks, you do too.” 

Once you both got past your little moment of small talk and shy silence at your doorstep, Gaster expressed that he wanted to take you somewhere, and you didn't hesitate leave with him. Like last time, he didn't talk much along the way, but he seemed rather excited when he reached the destination, which was the restaurant of the resort close by the lab. You'd seen this place many times, but you'd certainly never been able to afford eating there. 

“Forgive me if this isn't that exciting... But I thought this would be a relaxing place.” 

“Oh no it's great! I've always wanted to try the food here but it's... uh...” you trailed off, feeling a little guilty realizing you assumed he'd be paying the whole bill. 

“Expensive?” Gaster chuckled under his breath. “Don't worry about that. I can afford it. I promise.” His smile was genuine; his pupils so bright and lively. You smiled timidly as he escorted you inside, taking the left turn towards the restaurant that you've never taken before. 

The host—a hulking green fish monster—greeted you both. “Good evening Doctor Gaster! And... the human?” They looked at you inquisitively, and you shrunk. 

You tried to quickly think of something to say that wouldn't embarrass the doctor, though he beat you to the punch when he responded, “my date,” without any falter in his cheerful expression. Your face turned beet red immediately. 

The host's eyes widened for a moment, but then smiled big big grin. “Pick any table you like and we'll be right with you.” 

Gaster glanced at you, and just as quickly his smile turned into a concerned frown. “H-How about the back?” You nodded quietly and you followed him to the very last table in the corner of the room. You couldn't help but noticed as you passed the other monsters in the dining room, their eyes followed you until you sat down. The moment Gaster sat across from you, he leaned in towards you nervously, softly asking, “A-Are you alright? Are you... Are you ashamed to be seen with me?” 

There was heartbreak forming in his eyes, and you-almost-too loudly responded “NO! No... Not at all. I thought, actually, uh... You'd be the one ashamed to be seen with me...” Your head slunk into your shoulders. 

Gaster blinked several times, puzzled. “Why ever would I be?” 

“Because... Isn't it weird for a monster to date a human? Isn't that why everyone's looking at us?” 

“O-Oh, oh noooo....” Gaster trailed off, his eyes darting around aimless they landed on the approaching waiter. He set two glasses of ice water on the table, followed by two menus, and strolled away once more. Gaster didn't hesitate to pick up a menu and change the conversation, smiling again. “Please order anything you want, and don't worry about prices.” 

You took a sip of water as you opened the menu, pushing Gaster's odd response into the back of your mind. You trusted him, so you had no reason to doubt him if he said he wasn't embarrassed about you. It was a harder to believe him that it was really okay to order anything; you nearly spit out your water when you saw the prices. “O-Oh my god, are you sure?” 

“Positive,” Gaster reassured you with a big smile. You couldn't doubt his smile. 

Most everything on the menu sounded enticing. You managed to narrow down what you were most eager to try by the time the waiter showed up again. When it was Gaster's turn to order, he simply said, “the usual, please.” Before you had the chance to ask him what he was getting, Gaster had plopped his hands down onto the table and said, “I hope this is not presumptuous but... Despite all the time I've known you working in the lab I feel like I've so much more to learn. That is, I can study your soul plenty but it doesn't tell me anything about your past. If it would be alright with you, I was wondering if you would tell me more about your life on the surface, before you came down here?” 

You weren't quite sure where to begin—there was so much to cover. You began describing your home and your family, your friends, and then you talked about your education and what do you did for a living. Your were jumping around subjects as you thought of them, making you worry you were being confusing. However, Gaster seemed very enthralled in what you had to say, nodding with quiet “mhm”s as to not interrupt. You played with your hair as a bit of melancholy set in, coming full circle in your stream of memories.“Ah.. Yeah I guess I just... Still miss my family and friends sometimes.” 

“That's understandable,” Gaster said, “And all the more motivation for me to discover a peaceful way to free the underground. I'd like you to see your family again.” 

“I'd like to introduce you to them, too.” You smiled. Gaster's cheeks gained a hint of purple. 

Not long after your meals had arrived. You stuttered out a “thank you” as a beautifully presented dish was set down in front of you, almost too gorgeous to eat if not for the fact the aroma was even better. You tore your eyes away from it to observe what was set in front of Gaster—nothing more than a basket of french fries and ketchup on the side. You furrowed your brow. “That's all you wanted?” 

Gaster was already dipping one of the fries. “Yes. Is that strange to you?” 

“I mean it's just... you could get that at Grillby's over in Snowdin. You wouldn't rather have something fancier..?” 

Gaster chuckled. “Grillby's is no place for someone like me. This atmosphere is more pleasant. And no, I actually like this best.” He popped the fry into his mouth. Truthfully, you'd only ever seen Gaster eat things like pastries while he was working (you had thought that perhaps he was enthusiastic about supporting spiders). Since monster food worked so differently than human food, there were really no consequences to eating nothing but junk food. If this meal was “usual” for Gaster, then you could safely deduce junk was his preference. There was something endearing about that. 

You finally tasted a bite of your own meal, and it was more delicious than you had imagined. You had to restrain yourself from scarfing it down far too quickly, and instead take the time to savor the best food you've ever had in the Underground. You didn't realized you were entirely distracted by it until you heard Gaster ask, “so I take it you like it?” 

You looked up from your plate and swallowed quickly. “Oh, yeah! Yeah it's amazing!” 

“So it was a good choice taking you here?” 

“Absolutely. I really appreciate it.” You were both smiling at one another in goofy, doting manner until you continued eating the rest of your plate in comfortable silence. The classical music playing and the gently murmur of other monsters talking was relaxing. Gaster wasn't wrong about it being much more sophisticated than the atmosphere of Grillby's. It was a nice change of scenery. 

When you both finished, Gaster asked if you wanted anything else, to which you responded “oh no no, I'm full.” You thanked him again before the waiter came back and handed Gaster the bill. He barely gave it a glance before handing over payment, along with what you noticed was a very hefty tip. It's not that you didn't think being Royal Scientist wasn't a well-paying job, so much that it slipped your mind since you never saw Gaster flaunt his wealth—in fact, this was the first time you saw him flash such a large sum of money, which he just generously gave away. For such an aloof person socially, Gaster had quite an amount of hidden compassion. 

Gaster led the way out and you followed at his side. You tried to ignore the other monsters staring at you again, but it still made you a little uncomfortable until you were back outside. 

“That was really nice. Thank you again, Doctor Gast- I mean, Gaster.” you blushed in embarrassment. 

Gaster chuckled under his breathe. “You're welcome. I had a pleasant time getting to know you better. You're...” he fidgeted for a moment, his own cheeks starting to blush, “you're very interesting. I-I always thought you were interesting.” 

“Th-Thank you.” you looked down, shyly accepting the compliment, wondering just what kinds of “interesting” Gaster thought you were and how long he'd thought so. It seemed as though he'd had feelings for you for quite a while. If that's the case, he was good at hiding it. 

You both remained silent for a few long minutes, looking down as you faced one another. You weren't quite sure what to do next, whether you should invite Gaster over, or—

“S-So, uh...” Gaster started, fidgeting more and more as he spoke, “Did you want to... Sp-Spend some more time together?” he looked overly-concerned suddenly. “Is that too imposing of a question? You're certainly not obligated if you don't want-” 

“I would like to.” you smiled, taking both of Gaster's hands into your own. His face turned quite purple, as an expression of relief swept across his face. His claws curled around your hands; you felt them trembling ever so subtly. “Could we go to your place?” you asked, perhaps because it was the most simple thing you could think of, and perhaps just as much because you were really curious about what it looked like. 

“My place..? It's not very exciting... You wouldn't be too bored?” 

“I was thinking we could just... talk, and relax.” 

“Well... alright. If that's what you would like.” Gaster let go of your hands and led the way silently. 

You really had no idea what to expect in terms of location. He led you back through the resort and past the Core, towards the capital. You could see Asgore's castle in the distance. Before you knew it, he had stopped in front of a quite mundane looking white house. The architecture was minimalistic and modern, but so were all the other buildings surrounding it. 

“This is it.” Gaster said, approaching the door and unlocking it. Your heart raced as you stepped inside behind him, for that split second imagining something crazy like a second laboratory or something luxurious as the castle. It was more shocking that what you saw was... pretty average looking. There was some nice furniture, all sleek and black, a modest sized TV, an overall modestly decorated living room. The bigger surprise was the mess of papers that littered just about every piece of furniture. That was quite a jarring difference from his office in his lab, everything it contained being perfectly sorted away. 

“I apologize about the mess...” Gaster could tell you were looking at it, which you realized too late was very obvious.“I do a lot of planning and research in my leisure time, and it just ends up all over. I also haven't exactly... had company in quite some time.” He had already gone to the couch and was hastily stacking the papers into a pile, setting them on the coffee table. 

“Oh, no, it's okay! Don't worry about it! Honestly your house is really nice.” You sat down on the couch he cleared off for you. Gaster was still trying to fix up the surrounding mess. You felt a little guilty that he was so embarrassed about it.“You really don't need to fix anything, really, I don't mind at all. This is nothing compared to my bedroom!” you joked, eliciting Gaster to stop and smile at your comment, and finally sit down beside you. He laughed nervously. 

“Now you see what a disaster everything would be in the lab if I didn't have you there helping me.” He was blushing, averting his eyes from you. His knees were pressed together and he was fidgeting—a very familiar scene from the last time you were all alone with him. You promptly scooted closer to him until your thigh brushed against his. His eyes darted to the source of contact immediately. 

“Heh, I wouldn't mind... helping you out here. I mean, if you were okay with me coming back and everything...” 

Gaster's eyes widened in some incredulous way. “O-Of course...” His voice was almost a whisper. 

It was becoming painfully evident he was lonely. He was royal scientist, sure, but it seemed that his work left very little space for a social life—or did he even have any other life but science? The documents scattered around you suggested not. You tried not to frown, but frankly, you felt bad for him. 

“Hey Gaster... I know you work really hard and everything, but... have you ever considered giving yourself a break?” 

“I did,” he smiled nervously, tilting his head to the side as he looked at you, “I mean, I am. Right now, with you.” 

That wasn't exactly what you meant, but you didn't have the heart to shut such a sentiment down, so you nodded. “Right. That's true.” 

Gaster looked down sheepishly. “This is my first time.” You expected him to say something further or clarify that statement, but he did not. 

“Your first time...?” you asked, after several long seconds of silence. 

He turned to face you again. “On a date.” 

Your eyes widened and you felt a jolt in your chest. Suddenly, that strange behavior in the restaurant all made sense—the other monsters were not looking at you strictly because you were a human, but because Gaster had shown his face publicly with a date for the first time. It was bizarre, though. Not that Gaster was elderly, but he was certainly old enough to have had at least some sort of prior romantic encounters. More importantly though, he was Underground-famous—the Doctor Gaster—it's absolutely impossible not a single monster has ever been interested in him... right? 

“Th..There's never been anyone interested in you?” 

“Oh there certainly has been,” Gaster shook his head, “I've simply never found the time or purpose for frivolous romantic affairs. Frankly, I've never been interested in anything but my work.” 

“But... you're interested in me?” 

“W-Well...” Gaster stammered, tapping the tips of his claws against one another, “You are my work.” 

Feeling your face turn embarrassingly red, you looked down to the floor. It was true, and logical. If Gaster was only so enthralled by his experiments, how appropriate it was for him to be enamored with his most important experiment yet—your soul, your Determination, your human body, you—nearly everything he's worked on since you were brought to his lab has involved you. The epiphany overtook you like a wave, leaving you in stunned silence. 

“I-I'm sorry.. is that perturbing to you? Perhaps I was being too forward. I would understand if you don't want to-” 

“No,” you interrupted, “no, Doctor Gaster—I mean, Gaster-” you stumbled over your words, until finally you decided words weren't the best way to express yourself. You lurched forward and threw your hands around his shoulders, pulling him close so you could plant a kiss against his muzzle. His eyelids fell half-lidded dreamily almost immediately as he gently slipped his hands around your waist. Every inch you leaned closer to him he would move an inch back, until finally, he was laid on the bottom of the couch with you on top of him, straddling his waist. You pulled back from your kiss, admiring your ability to get the doctor so easily pinned down, looking up at you affectionately over his glasses that were now crooked on his face. His cheeks were already flushed a deep purple. 

“Oh, human...” his voice was breathy, “After what we did the last time, I couldn't face you for a week because I could not stop thinking about it...”

It made you giddy that he finally brought up the sex, especially the mental image of Gaster getting too hot and bothered by the thought of it that he couldn't even look at you in a professional setting. You grinned. “Do you want to do it again?” 

“I-If you want to, th-then yes, I do,” Gaster stammered. You could already feel him getting hard under you. You shifted down his lap enough to make the zipper of his pants accessible. While you pulled his penis through, he whimpered and put his hands on his cheeks. You had to wonder—given that he told you you were his first date—were you also his first sexual partner? You knew that now wasn't really the time to ask a question like that, but when you gazed at that beautiful purple monster cock, you smiled deviously. If, hypothetically, you were the first, then you wanted to really rock his world and surprise him. 

You shuffled down more, parting his legs and ushering him to bed his knees to make space for you between them. He looked at you inquisitively, and let out a gasp when you planted a kiss onto the tip of his cock. 

“Is this okay with you? Putting my mouth on it?” you took a moment to ask. 

“O-Oh yes, of course..!” 

With his assurance, you pressed your lips back onto the tip, closing your eyes. It was such a dream come true to blow him, you wanted to savor it—really take it in slowly. There wasn't really any kind of taste to it. It felt smooth like soft like gelatin; you felt nervous that it was soft enough to bite in half, though upon recalling the sex you had with him, it couldn't possibly be that fragile. Even so, you were careful to keep your teeth from scraping it. The texture allowed for it to be lubed so easily by your saliva, letting your tongue and lips slide with no friction. It felt wonderful for you, and you knew it felt wonderful for him too by the sounds he was making in response. 

You swiveled your tongue around the tip in gentle circles, making Gaster let an almost purr-like sound. His purr became a moan when you slid your mouth down the length more and more. When your lips reached the top of the knot, you already had enough in your mouth to graze the back of your throat. That seemed like a good stopping point, and to start sucking up and down in a gentle, steady motion. 

After a couple minutes you finally opened your eyes to see how Gaster was looking. You weren't surprised to see that he was practically melting into the couch, arm thrown over his eyes and his other hand gripping the fabric of his shirt. His glasses had fallen off onto the floor. You had to force the corners of your lips not to curl into a smile, and keep your pace. 

Gaster's panting and moaning became louder as you felt his cock begin to pulsate. His tail, which was hanging off the side of the couch, began to beat against the side of the cushion. You eagerly took this as a signal to get more ambitious—you pushed your mouth even further down the shaft, trying to open as much as you could around the knot. You didn't get very far, but even the extra couple centimeters was enough to feel the head pushing further into your throat. Thanks to its softness it didn't hurt, but it still was a lot. Your saliva was streaming down the shaft and soaking the seat of Gaster's pants. 

Gaster's eyes shot open and he looked at you with concern. “H-Human! O-Oh my goodness—“ He lifted his hands towards you but paused halfway. He seemed to worry that he was hurting you, but you gave him a reassuring thumbs up, resuming your sucking. After a few seconds he smiled sheepishly and allowed himself to relax into the cushions again, moaning in pleasure. His eyes stayed open this time. 

“Ahh... I f-feel like, I'm going to come, i-if you...” he trailed off while he gazed at you, his face flushed bright purple. You definitely wanted that, absolutely. You swirled your tongue more, pumped faster, nearly triggering your gag reflex but you remained steadfast nonetheless. Your increasingly restless hands found their way to Gaster's thighs, grasping onto his pants. 

Soon enough Gaster's ragged panting erupted into a crying moan, and in tune with it, you felt him release inside your mouth. You froze immediately, savoring the feeling of the magic ooze filling your throat. There was a subtle, pleasant sweetness to it. With how much length you had in your mouth, you didn't have any choice but to swallow the bulk of it—not that it was a problem. Once you did that, you slid your lips up the shaft and gently off the tip, collecting any remaining cum. You licked your lips.

Gaster was giving you an incredulous look, as though he couldn't believe what you did. He was quiet, though his breathing was still heavy, his chest still rising and falling rapidly. “I...I don't even know what to say...” he sounded almost out of breath. 

“Did you like it?” 

“Y-Yes, it was wonderful,” he put his hands on his face again—as he does when you get him so flustered. “Th-Thank you.”

You giggle. “You're welcome, Gaster. It's fun to please you.” The magic forming Gaster's penis dissipated quickly, leaving only a glimpse of his skeletal pelvis through his open zipper. You decided to be polite and zip it back up. 

“I... I just can't believe it,” Gaster began to sit back up, leaving his legs where they were as to rest his arms on his knees. His tail wrapped around his ankles. “A human like you, attracted to me...?” His snout was pointed down piteously. 

You inched closer to him, taking his hands into yours. “It's fascinating, isn't it?” you smiled sweetly, your eyes half lidded. 

“...Yes. Most definitely,” he smiled back, seemingly reassured. You planted a long kiss on his muzzle. You could feel his tenseness melt away as his knees fell down to the side and his arms wrapped around you to pull you closer and into his now crisscrossed legs. You reciprocated his embrace, cooing as you continued to kiss his lip-less mouth. One of his claws began to burrow into your hair, running up and down your scalp in gentle motions. Once again, it felt so amazing and otherworldly to feel the gentle touch of a monster who could easily tear you to shreds. To you, that was something fascinating—how human monsters really were at heart. For this reason, it almost seemed silly Gaster was so surprised that you had the capacity to fall for him. 

When the kiss parted, you both gazed at one another dotingly in a few seconds of silence. 

“Looks like you'll just have to do some more experiments with me to answer all your questions about human attraction,” you joked. 

“So there will be another date, then?” Gaster's eyes were bright and full of hope. 

“Yeah,” you sighed happily, “But this one's not over yet, is it?” 

“O-Oh, n-no, not unless you want it to be..!” Gaster scrambled for his glasses suddenly, fixing them back on his face, “Though I can deduce your question implies that you don't want it to be so in that cause I um...” he began to fidget and avert eye contact, which of course was cute and amusing. “You're, uh... welcome to s-stay the night i-if you fancy... We could perhaps watch a movie...” 

You blushed. “I'd love to.” You gave Gaster a loving kiss on the cheek.


End file.
